Wireless cellular telecommunications networks are known. The area covered by the network is divided up into a number of cells each of which has base station. User equipment in the cells are able to communicate with the base stations using radio frequencies. The user equipment can take any suitable format and is often a mobile terminal. The wireless network can be connected to other wireless networks using the same or different standards as well as to wired networks.
A number of different standards have been proposed or are known which govern the communications within the cellular network. GSM (global system for mobile communications) is one such standard which uses a time/frequency division multiple access approach. This is a so called second generation standard. Third generation standards such as UMTS (Universal mobile telecommunications system) and W-CDMA (wideband code division multiple access) are currently being proposed. At least some of these third generation systems propose to use a code division multiple access technique.
In the 3rd Generation Partnership Project, Technical Specification Group Services and System Aspects; Architecture Principles for Release 2000, 3G TR 23.821 which is incorporated by reference, a system is described. This system has a media gateway MGW and a MSC server which communicate via an H.248/MEGACO protocol. This is a protocol which has been developed by ITU-T and IETF. H.248 is the ITU-T name for it and MEGACO (media gateway control) is the IETF name for it. In this document it will be referred to as the H.248 protocol. The protocol has been developed for networks where the user plane and the control plane are separated, for example in H.323 servers and gateways. This document describes a system in which there are amongst other entities a media gateway MGW and a mobile services switching centre MSC server. These two entities are directly connected to each with the MGW interfacing with the radio access part of the network and other MGWs, and the MSC server being connected to a number of entities such as the radio access part of the network, a gateway MSC, and various applications and services.
The MGW Is a distributed network element which is used for user plane transmission. The MSC server is a centralised network element. H.248/MEGACO is used as a control protocol between the MGW and the MSC server.
In use both the MGW and the MSC server have to reserve resources. The resources are basically user plane termination points and connections between them. Also some properties related to user plane termination points are also regarded as resources. When a call requires something for the user plane in the media gateway, the MSC server requests resources such as termination points, connections or the like. The MSC server and the MGW have a common understanding of the reserved resources.
However, the inventors have appreciated that the current proposals do not address the difficulties which would be caused in there is a mismatch of resources reserved in the MGW and the MSC server. For example, the resources in one of the entities may be released whilst remaining reserved in the other entity. If this occurs a number of times, resources which are not being used are reserved and cannot be used. This effectively reduces the available capacity of the entity. Clearly this is undesirable.